Sialic Acid-Extended Release (SA-ER, aceneuramic acid, UX001) is an extended release formulation of sialic acid (SA, also known as N-acetylneuraminic acid or NANA). The SA-ER is currently studied as a substrate replacement therapy for patients with GNE myopathy. The investigators plan to study the SA-ER compound in a cohort of five patients with GNE-related thrombocytopenia.

The investigators identified 5 affected individuals (3 males and 2 females from three families, age 19-40 years) with GNE-related thrombocytopenia . All subjects will receive 2 gram SA-ER, three times per day for a total daily dose of 6 grams (6,000 mg). The dose should be administered with food (i.e. within 30 minutes of a meal or snack).

Efficacy will be evaluated by improvement in clinical and laboratory assessments. Results from Baseline assessments will be compared with those of post-treatment assessments with efficacy conclusions based on improvement between Baseline and the last scheduled assessment. Safety will be evaluated by the incidence and frequency of adverse events, including clinically significant changes from Baseline to scheduled time points in:

• Vital signs.
• History and physical examination findings.
• Laboratory evaluations.
• Serum uric acid levels and urinary excretion of uric acid.

Inclusion Criteria:

• Patients with GNE-related macrothrombocytopenia in the investigated family

Exclusion Criteria:

• non consenting for this study
• pregnancy